One vertex per element, one color per generator, with an edge from x to x·s.
(3,7)(6,8)(9,10,14,20,16,19,15,31)(11,21,25,35,24,34,30,17)(12,26,28,37,27,39,13,18)(22,32,38,33,23,36,29,40)(2,5)(3,7)(9,11)(10,17)(12,23)(13,29)(14,30)(15,25)(16,24)(18,36)(19,35)(20,34)(21,31)(22,27)(26,33)(28,38)(32,37)(39,40) involution — undirected(1,2)(3,6)(4,5)(7,8)(9,12,15,13,16,27,14,28)(10,18,20,26,19,37,31,39)(11,22,25,38,24,23,30,29)(17,32,34,40,35,36,21,33)(2,5)(6,8)(9,13,15,27,16,28,14,12)(10,18,31,39,19,37,20,26)(11,23,30,38,24,22,25,29)(17,33,34,32,35,40,21,36)(1,3,4,7)(2,6,5,8)(10,19)(11,24)(12,27)(13,28)(20,31)(25,30)(32,36)(33,40)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.